Deblocking contact lenses

ABSTRACT

A method and apparatus for removing a polymeric contact lens from a mold comprising lowering the temperature of the contact lens with a cryogenic material, such as liquid nitrogen, to a temperature and for a time sufficient for the lens to release from the mold without the application of external forces.

This application claims priority to provisional application Ser. No.60/325,779, filed Oct. 13, 2000, which was converted to a provisionalapplication by petition from non-provisional application Ser. No.09/428,067, filed Oct. 27, 1999.

FIELD OF THE INVENTION

The invention relates to a method for use in manufacturing ophthalmiccomponents, such as a contact lens. Specifically, the invention relatesto a method and apparatus for removing a contact lens from a mold, aprocess also known as “deblocking” a contact lens.

BACKGROUND OF THE INVENTION

The most common materials currently utilized in manufacturing softcontact lens are polymers and copolymers of 2-hydroxyethyl methacrylate(HEMA). These hydrophilic polymers move well on the eye and providesufficient oxygen permeability for daily wear. Some HEMA soft contactlenses have been approved for extended periods of wear up to 7 days.However, such extended wear may result in comeal swelling anddevelopment of surface blood vessels in the sclera.

Research for improved oxygen permeable polymers has led to thedevelopment of polymers containing silicone groups. A variety ofsiloxane-containing polymers exhibit high oxygen permeability. Becauseof their oxygen permeability siloxane-containing polymers show greatpromise as the next generation of contact lens polymer. Unfortunately,siloxane-containing polymers possess physical characteristics that havethus far hindered their ascension to dominance in the field of contactlenses.

In layman's terms, siloxane-containing polymers are sticky. Contactlenses made of these polymers are hydrophobic and tend to adhere tovarious surfaces, severely complicating the manufacturing process. Forexample, a siloxane-containing lens will adhere to surfaces during thetransfer of the lens from point to point during the manufacturingprocess. One particular point in the manufacturing process that oftencauses problems is removing the lens from the mold, a step that is alsoknown as “deblocking” the lens.

Those familiar with the art know that a contact lens mold typicallyconsists of a base curve (convex) mold half and a front curve (concave)mold half formed from a polymer. In the siloxane-containing lensmanufacturing context, polyolefin (e.g., polypropylene) molds are mostcommonly used. The front curve and base curve mold halves are fittedtogether to form a small crescent shaped mold cavity between the basecurve mold half and the front curve mold half. Introducing a fluidmonomer to the front curve mold and then sandwiching the monomer withthe base curve mold forms a fluid monomer in the shape of a lens. Thechoice of monomer and the shape of the crescent shaped cavity determinethe optical properties of the lens. The monomer is then polymerizedthrough heat treatment, light treatment or other polymerizing process,thus forming a soft contact lens.

After the lens is formed the mold halves are separated. Contact lenses,especially siloxane-containing lenses, regularly stick to one of themold halves. In the siloxane-containing lens context, the lenses tend toattach to the front curve mold half. Those skilled in the art typicallyrefer to a front curve or back curve mold half as a “mold.” For the restof this discussion the terms mold half and mold will be usedinterchangeably unless the context requires otherwise. Those skilled inthe art will readily recognize such context.

The reason for the particular attachment to the front curve mold is notcompletely understood. The adherence of the lens is probably related toa combination of the lens mold interface phenomena and physicalproperties of the lens including the mold surface morphology, internalstress build up within the lens (or distortion) and the stressdistribution and the wettability of the lens material.

Under dry conditions it is difficult to separate a siloxane-containinglens from a mold surface due to adhesion between the lens and moldsurface. Lenses can be forced to separate from the mold surface byapplying a force, such as with a pair of tweezers. Nevertheless, theapplication of such force to peel a lens off of a mold surface oftenresults in damage to the lens. For example, the lens may becomescratched, distorted or torn, each of which renders it useless.

The adhesion between the lens and mold surface can be weakened when themolecules of the lens polymer become mobile. For example, the moleculesmay become mobile by adding heat or chemicals such as a solvent.Accordingly, an alternative method for removing a lens from a moldsurface involves the use of a solvent such as isopropyl alcohol (“IPA”).In this method IPA is applied directly to the lens as it adheres to themold surface. The solvent swells the lens and helps reduce the forcesholding the lens to the mold surface. The lens may then be removed fromthe mold surface.

Although this method of deblocking reduces the likelihood of damage tothe lens, the collection and disposal of used solvent carries both aneconomic and environmental price. For example, used IPA may beclassified as hazardous waste in some states. Accordingly, a need existsfor an improved method for removing a contact lens from a mold.

OBJECT AND SUMMARY OF THE INVENTION

An object of the invention is to provide a non-mechanical method ofdeblocking a contact lens.

A further object of the invention is to provide a method of deblocking acontact lens that does not require a solvent.

A further object of the invention is to provide a method of deblocking acontact lens that does not damage the contact lens.

A further object of the invention is to provide a method of deblocking acontact lens that does not generate a potentially hazardous waste as aby-product

A further object of the invention is to provide a method of deblocking acontact lens using a cryogenic material.

An object of the invention is to provide an apparatus for use indeblocking a contact lens.

A further object of the invention is to provide an apparatus for use indeblocking a contact lens that may be used in a cryogenic deblockingprocess.

A further object of the invention is to provide an apparatus for use indeblocking a contact lens that does not damage the contact lens.

A further object of the invention is to provide an apparatus for use indeblocking a contact lens that allows substantial automation of acryogenic deblocking process.

A further object of the invention is to provide a carrier that canreceive a contact lens mold bearing a contact lens and transport saidmold and lens through a deblocking sequence in an efficient manner.

The invention meets these objects with a method for extracting a contactlens from a mold by lowering the temperature of the contact lens to atemperature sufficient to lessen adherence between the lens and the moldthen removing the lens from the mold. The lowering of the temperature ofthe contact lens is accomplished by direct or indirect contact with acryogenic substance, such as liquid nitrogen.

The invention also meets these objects with an apparatus to deblock andcollect contact lenses comprising a top plate for receiving a contactlens mold bearing a contact lens and a bottom plate for receiving thecontact lens. The contact lens mold is oriented within the top platesuch that the contact lens is free to fall to the bottom plate afterdeblocking through application of a cryogenic material. The followingsections set forth a preferred embodiment of the invention in which:

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a contact lens mold.

FIG. 2 is a perspective view of one embodiment of the deblockingapparatus according to the invention with a corner section removed.

FIG. 3 is a cross-sectional view of the apparatus section removed fromFIG. 2.

FIG. 4 is a perspective view of the apparatus section shown in FIG. 3.

FIG. 5 is a cross-sectional view of a deblocked contact lens on acontact lens holder.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is based upon the surprising discovery thatreducing the temperature of a contact lens may weaken the forces causingadherence of the contact lens, and specifically a siloxane-containinglens, to the surface of a mold.

The present invention is a method for extracting a polymeric contactlens from a mold. In its broadest aspects, the method comprises loweringthe temperature of the contact lens to a temperature sufficient toreduce adhesion between the lens and the mold to a point where removingthe lens will not damage the lens, and thereafter removing the lens fromthe mold.

Although the inventors do not wish to be bound by any particular theory,it appears that the step of lowering the temperature of the contact lenssubstantially reduces the molecular mobility of the contact lenspolymer. Depending upon the circumstances, the step of lowering thetemperature of the contact lens can comprise directly contacting thecontact lens with the cryogenic substance, or contacting the mold with acryogenic substance while the lens is in contact with the mold.

In particular, the cryogenic substance can be anything which, whenplaced in contact with either the mold or the lens, will reduce thetemperature to the desired degree. The cryogenic substance is preferablyselected from the group consisting of liquid nitrogen, liquid helium,liquid carbon dioxide, and solid carbon dioxide (“dry ice”), with liquidnitrogen being most presently preferred as having the optimumcombination of ease of use and economic availability.

As noted above, the method is particularly useful when the contact lensmaterial is a siloxane-containing polymer, more particularly asiloxane-containing hydrogel polymer.

In another aspect, the method comprises bringing the contact lens intocontact with a cryogenic substance for a time sufficient to lower thetemperature of the lens to a temperature sufficient to reduce adhesionbetween the lens and the mold to a point where removing the lens willnot damage the lens. Thereafter, the method comprises separating thelens from the mold, and recovering the separated lens. Preferably, thestep of separating the lens from the mold comprises lowering thetemperature of the lens to a temperature at which the lens will releasefrom the mold without the application of external force to the lens. Asin the previous embodiment, the method can comprise either bringing thelens into contact with the cryogenic substance, or it can comprisebringing the mold with the lens therein or thereon into contact with thecryogenic substance, with the cooling of the mold being sufficient tocool the lens to the point at which it will release as desired from themold.

In another aspect, the invention comprises a method for extracting asilicon containing polymeric contact lens from a mold comprising thesteps of orienting a contact lens bearing mold upon a carrier with thecontact lens in a position to fall from the mold under the influence ofgravity. A contact lens collector is then positioned or situated in aposition at which it can collect a contact lens that may fall from theoriented carrier. The mold carrying the lens is then brought intocontact with the cryogenic substance which, as noted previously, causesthe lens to release from the mold and separate therefrom. The methodalso comprises collecting the lens following its separation from mold.

In another aspect, the invention comprises a method for manufacturingsilicon containing polymeric contact lenses. In this embodiment, themethod comprises bringing two mold halves together to form a lens mold;filling the mold with an uncured polymer (those familiar with polymerchemistry will recognize that this can also be a pre-polymer or a lowmolecular weight polymer, or a polymer that can be furthercross-linked); curing the polymer in the mold, usually by application ofheat or ultraviolet light depending upon the particular chemistry of thelens polymer; separating the mold halves from one another; and bringingthe mold half bearing the contact lens into contact with a cryogenicsubstance for a time sufficient to lower the temperature of the lens toa temperature sufficient to reduce adhesion between the lens and themold half to a point at which removing the lens will not damage thelens. Thereafter the method comprises separating the lens from the moldhalf and recovering the separated lens.

When a siloxane-containing lens attached to a polypropylene mold isplaced in a vessel containing a quantity of liquid nitrogen the lensseparates itself from the mold and falls to the bottom of the vesselafter a very short period of time and the polypropylene mold floats tothe top of the liquid nitrogen.

Upon warming, the lens releases any liquid nitrogen adhering to itssurface by giving off gaseous N₂. Any liquid nitrogen remaining in thecontainer likewise evaporates. The end result is a clean deblockedcontact lens without any troublesome waste byproducts, e.g. used IPA.

At this time, the physical mechanism of the cryogenic deblocking methodis not completely understood. The fact that a lens will peel itself offof a mold surface suggests that there is some negative force orenvironment created by lowering the temperature of the contact lenswhich assists in reducing adhesion at the interface. For example, it isspeculated that there may be a very small physical dimensional change inthe lens and mold surface that causes the lens to release.

The operation of the preferred embodiment of the apparatus of thepresent invention comprises forming a contact lens in a mold, separatingthe mold and placing the mold half bearing the contact lens within acarrier with the mold being oriented contact lens side down. Situatedunderneath the mold and directly beneath the contact lens is a contactlens collector, a structure designed to receive the contact lens. Liquidnitrogen is then applied to the side of the mold opposite the contactlens in an amount sufficient to lower the temperature of the contactlens to the point where it would automatically release from the mold andfall to the contact lens collector. The thus deblocked contact lens thenproceeds to subsequent steps in the manufacturing process.

The temperature sufficient to lower the temperature of the contact lensto the point where it would automatically release from the mold cannotbe precisely defined as it will depend the cryogenic material used, aswell as the materials used for the lenses and for the molds. One ofskill in the art will recognize that determination of a sufficienttemperature is easily obtained by only routine experimentation once thematerials are known. Typically, the temperature achieved with liquidnitrogen is sufficient to deblock commercially available lens materialsfrom a polypropylene mold. However, some mold materials may beincompatible with the present method. For instance, the method disclosedherein is may not be operable with molds made of certain grades ofpolycarbonate.

Referring now to FIG. 1, a cross-section of a typical soft contact lensmold 10 comprising a base curve mold half 12 and a front curve mold half14 is shown. As can be seen from FIG. 1, the base curve mold half 12 andthe front curve mold half 14 fit together to form a crescent shapedcavity. As discussed previously, placing a monomer in the crescentshaped cavity and polymerizing the monomer forms a contact lens 16.Typically, an excess of monomer is used to ensure a fully formed lens.Excess monomer results in a portion of the monomer being squeezed out ofthe mold. The excess monomer is separated from the contact lens 16 andretained within the overfill well 11 formed by the compression of thefront curve critical lip 9 to the base curve seal 8.

After the contact lens 16 is formed the mold is separated into its twohalves. Typically the contact lens adheres to the front curve mold.

In another aspect the invention is an apparatus for deblocking andcollecting contact lenses formed of hydrophilic polymers that tend toadhere to mold surfaces. In this aspect the invention comprises acontact lens mold and means, illustrated in the drawings as thereservoir 13, for cooling the contact lens mold 14 and the lens 16 thatis adhered to the mold 14. Although a front curve lens mold or a basecurve lens mold may be utilized in the invention, for purposes of thisdiscussion it will be assumed that the lens mold is a front curve lensmold 14. The means for cooling cools the mold 14 and the lens 16 to atemperature at which the lens 16 may be removed from the mold withoutdamaging the lens may encompass any known method for cooling such asplacing the contact lens and the mold to which it adheres within asufficiently cooled enclosure. Such an approach, however, is cumbersomeand inefficient and does not lend itself to integration in an automatedmanufacturing process.

A preferred embodiment of the invention is illustrated in FIG. 2 whereinthe lens mold 14 is retained by a top plate 20. The top plate 20 issituated above the bottom plate 22. The bottom plate 22 is substantiallyparallel to the top plate 20 and retains a lens collector 26. The topplate 20 and the bottom plate 22 are aligned so that the lens mold 14and the lens 16 are in axial alignment with the lens collector 26retained by the bottom plate 22.

The side of the lens mold 14 opposite the lens 16 is formed to create areservoir 13. A cryogenic material (“cryogent”) is introduced to thereservoir 13 (preferably at its center) thereby cooling the mold 14 andthe lens 16 to a temperature sufficient for the lens 16 to release fromthe mold 14 and fall to the lens collector 26. The cryogenic cooling ofthe mold also has the effect of shrinking the overfill well 11 therebyeffectively trapping the excess monomer and removing it from theprocess. The cryogenic substance is preferably selected from the groupconsisting of liquid nitrogen, liquid helium, liquid carbon dioxide, andsolid carbon dioxide (“dry ice”), with liquid nitrogen being mostpresently preferred as having the optimum combination of ease of use andeconomic availability.

Referring now to FIG. 3, another embodiment of the invention is acontact lens carrier 18. The contact lens carrier according to theinvention comprises two plates: a top plate 20 and a bottom plate 22.

The top plate 20 is defined by a top surface 19 and a bottom surface 21separated by a predetermined width. The top plate 20 also possesses aplurality of holes 24, in this instance twelve, for receiving molds 14bearing contact lenses 16. The contact lens mold received by the topplate 20 will be a front curve lens mold in most instances. Top plate 20can also receive back curve lens molds with appropriate modifications.FIG. 3 shows a mold 14 oriented within the top plate hole 24 to placethe contact lens 16 at a location intermediate the top plate top surface19 and the top plate bottom surface 21. This orientation suspends thecontact lens 28 above the bottom plate 22.

The top plate 20 also includes a retaining device to secure thepositioning of the molds 14 during the deblocking process and duringsubsequent downstream manufacturing processes. Any suitable retainingdevice may be used to secure the positioning of the molds 14. Forexample, a retaining plate having holes corresponding to the top plateholes 24 may be placed above the molds. Likewise, the perimeter of thetop plate holes 24 and the molds 14 may be molded or machined such thatthe molds 14 “snap-fit” into place.

FIG. 3 and FIG. 4 show a preferred embodiment of such a retaining devicecomprising a flexible tab 30 having a notch 32 that receives the outerflange 15 of the mold 14. A pair of flexible tabs 30 may retain eachmold 14. Alternatively, the molds 14 may be oriented such that the outerflange 15 of one mold overlaps the outer flange 15 of another moldthereby reducing the number of flexible tabs 30 required to effectivelysecure the positioning of the molds. The molds 14 in FIG. 3 and FIG. 4are secured by such an overlapping arrangement.

In some instances the contact lens may not separate itself from themold. In these instances an application of a slight external force, suchas tapping the mold, should suffice to dislodge the lens. The tappingforce may be applied manually as with a small mallet. Alternatively, thetapping force may be automated. For example a small spring loaded pistonmay be placed in contact with the mold and automatically triggeredthereby sending a small shockwave through the mold.

During deblocking, liquid nitrogen is applied to the side of the mold 14opposite the contact lens 16 as shown in FIG. 3. The liquid nitrogensubstantially reduces the temperature of the mold 14 and the contactlens 16. The contact lens 16 separates itself from the mold 14 and fallstoward the bottom plate 22. The small quantity of liquid nitrogenapplied to the mold 14 quickly evaporates leaving behind only a cleanand deblocked lens mold.

In the preferred embodiment shown in FIG. 3, the top plate 20 and thebottom plate 22 are attached by a set of locking pins 17 that arereceived by both the top plate 20 and the bottom plate 22. Preferably adistance separates the top and bottom plates. In the preferredembodiment shown in FIG. 3, washer-like spacers 23 retained by thelocking pins 17 separate the top plate 20 and the bottom plate 22.Alternatively, the spacers may be omitted and the top plate and thebottom plate may be in direct contact with each other. In this instancethe thickness of the top and bottom plates may need to be increased toallow room for additional components that primarily reside between thetwo plates. These additional components are discussed below.

Although any type of three dimensional object may serve as a spacerbetween the top and bottom plates, the washer-like spacers 23 shown inFIG. 3 are preferred because they are easily removed and are adjustablewhen used in conjunction a set of locking pins 17. Likewise, anyattaching mechanism such as nuts and bolts, screws, etc., may be used tosecure the positioning of the top plate 20 with respect to the bottomplate 22, however, multiple locking pins, in conjunction withwasher-like spacers, provide sufficient stability and desiredadjustability.

Referring now to FIG. 4 and FIG. 5, the bottom plate 22 is situatedbeneath the top plate 20. When the contact lens 16 is deblocked andfalls toward the bottom plate 22 the deblocked lens 16 is received by acontact lens collector, generally indicated at 26. In a preferredembodiment shown in FIG. 5, the bottom plate 22 possesses a plurality ofcontact lens collectors 26 retained within a plurality of bottom plateholes 25. The contact lens collector 26 comprises a generallyhemispherical structure 32 enclosed by an integrated flange 34. Thecontact lens collector 26 is preferably made from a polymer and ismolded to “snap-fit” within bottom plate hole 25 as generally indicatedby the “tongue and groove” junction 38 shown in FIG. 5. The generallyhemispherical structure 32 is convex and extends upward from the flange34 to a point intermediate the top plate surface 19 and the bottomplate.

It is to be understood that numerous other orientations are possible forthe bottom plate and the contact lens collector. For example, thecontact lens collector could comprise a table-like structure rather thana hemispherical structure. Likewise, the bottom plate and the contactlens collector could be a single integrated unit. Furthermore, thegenerally hemispherical structure 32, shown in a convex orientation inFIG. 5, could be concave to receive a contact lens from a base curvemold.

The generally hemispherical structure 32 shown in FIG. 5 preferablypossesses several holes or perforations 36 for reducing the effectivesurface area of the hemispherical structure 32.

The top plate 20 and the bottom plate 22 are separated after deblockingis completed. The bottom plate 22 and the deblocked contact lens 16proceed to subsequent points in the manufacturing process. After theinitial observation that temperature reduction alone could deblock acontact lens, several more experiments were conducted to explore whateffect, if any, this deblocking method had on a lens. These experimentsproceeded as follows.

One hundred and fifty six (156) lenses with a Rx of−1.75 aremanufactured according to Example B5 of U.S. Pat. No. 5,760,100 andstaged within their molds and plastic bags for approximately 25 daysprior to mold separation. Upon separation, the lenses and the frontcurve molds to which they adhered are separated into three groups eachcontaining 52 lenses: A (Example 1), B (Example 2), and C (Example 3),for further testing. No lenses are damaged due to mold separation.

EXAMPLE 1 Prior Art

The Group A lenses are deblocked using IPA deblocking techniques knownin the art. Each lens successfully separates from its mold surface bybathing the lens in IPA. All lenses exhibit good clarity, sphericity,and flex.

EXAMPLE 2

The Group B lenses are deblocked using direct contact with liquidnitrogen (i.e. liquid nitrogen was applied directly to the lens). Eachlens separates from its mold surface, taking an average of 9.8 seconds.All lenses deblocked by this technique exhibit good clarity, sphericity,and flex. Furthermore, the deblocking technique does not result indetrimental changes in Rx measurements, mechanical properties (modulus,maximum stress, maximum elongation, and thickness), ion permeability, orXPS.

EXAMPLE 3

The Group C lenses are deblocked using indirect contact with liquidnitrogen (i.e. liquid nitrogen was applied to the side of the frontcurve mold opposite the contact lens). Forty-seven out of the fifty-twolenses separate from the mold surface, taking an average of 16.5seconds. The failure of the five lenses to separate may have beenpartially due to excess lens material in the mold. All lenses deblockedby this technique exhibit good clarity, sphericity, and flex.Furthermore, the deblocking technique does not result in detrimentalchanges in Rx measurements, mechanical properties (modulus, maximumstress, maximum elongation, and thickness), ion permeability, or XPS.

As stated previously, the invention is preferably practiced usingpolypropylene molds. Because polypropylene is a known insulator, thedifference in time between Group A (direct contact; 9.8 s) and Group B(indirect contact; 16.5 s) is most likely due to differences in thecooling efficiency of the two cooling methods, as well as location forfreezing. One of skill in the art will recognize that the placement ofcontact of the cryogenic material with the mold will affect the coolingefficiency. Only routine experimentation is necessary to determine theoptimum placement. Currently, it is preferred to place the cryogenicmaterial immediately above the contact lens in the mold as explainedabove with reference to FIG. 2.

The invention has been described in detail, with reference to certainpreferred embodiments, in order to enable the reader to practice theinvention without undue experimentation. However, a person havingordinary skill in the art will readily recognize that many of thecomponents and parameters may be varied or modified to a certain extentwithout departing from the scope and spirit of the invention.Furthermore, titles, headings, or the like are provided to enhance thereader's comprehension of this document, and should not be read aslimiting the scope of the present invention. Accordingly, only thefollowing claims and reasonable extensions and equivalents define theintellectual property rights to the invention.

1. A method for extracting a polymeric contact lens from a mold, themethod comprising: lowering the temperature of the contact lens with acryogenic substance to a temperature sufficient to reduce adhesionbetween the lens and the mold to a point where removing the lens willnot damage the lens, and thereafter removing the lens from the moldwithout the application of external force to the lens.
 2. The method ofclaim 1 wherein the step of lowering the temperature of the contact lenscomprises directly contacting the contact lens with the cryogenicsubstance.
 3. The method of claim 2 wherein the cryogenic substance isselected from the group consisting of liquid nitrogen, liquid helium andsolid carbon dioxide.
 4. The method of claim 1 wherein the step oflowering the temperature of the contact lens comprises indirectlycooling the contact lens by contacting the mold with the cryogenicsubstance while the lens is in contact with the mold.
 5. The method ofclaim 4 wherein the cryogenic substance is selected from the groupconsisting of liquid nitrogen, liquid helium and solid carbon dioxide.6. The method of claim 1 wherein the contact lens comprises asiloxane-containing polymer.
 7. A method for extracting a siloxanecontaining polymeric contact lens from a mold, the method comprising:bringing the lens into contact with a cryogenic substance for a timesufficient to lower the temperature of the lens to a temperaturesufficient to reduce adhesion between the lens and the mold to a pointwhere removing the lens will not damage the lens, separating the lensfrom the mold without the application of external force to the lens, andrecovering the lens.
 8. A method according to claim 7 wherein thecryogenic substance is selected from the group consisting of liquidnitrogen, liquid helium and solid carbon dioxide.
 9. A method accordingto claim 7 wherein the step of separating the lens from the moldcomprises lowering the temperature of the lens to a temperature at whichthe lens will release from the mold without the application of externalforce to the lens.
 10. A method for extracting a siloxane containingpolymeric contact lens from a mold, the method comprising: indirectlycooling the contact lens by bringing the mold into contact with acryogenic substance for a time sufficient to lower the temperature ofthe lens to a temperature sufficient to reduce adhesion between the lensand the mold to a point where removing the lens will not damage thelens, separating the lens from the mold without the application ofexternal force to the lens, and recovering the lens.
 11. A methodaccording to claim 10 wherein the cryogenic substance is selected fromthe group consisting of liquid nitrogen, liquid helium and solid carbondioxide.
 12. A method according to claim 10 wherein the step ofseparating the lens from the mold comprises lowering the temperature ofthe lens to a temperature at which the lens will release from the moldwithout the application of external force to the lens.
 13. A method forextracting a siloxane containing polymeric contact lens from a mold, themethod comprising: orienting a contact lens bearing mold upon a carriersuch that the contact lens may fall from the mold; situating a contactlens collector so as to collect a contact lens which may separate fromthe mold and fall; indirectly cooling the contact lens by causing themold to come into intimate contact with a cryogenic substance; causingseparation of the lens from the mold without the application of externalforce to the lens; and collecting the lens.
 14. A method according toclaim 13 wherein the step of causing separation of the lens from themold comprises causing the mold to come into intimate contact with acryogenic substance for a time sufficient to lower the temperature ofthe lens to a temperature sufficient to reduce adhesion between the lensand the mold to a point where the lens will automatically separate fromthe mold and fall to the lens collector.
 15. A method according to claim14 wherein the cryogenic substance is selected from the group consistingof liquid nitrogen, liquid helium and solid carbon dioxide.
 16. A methodfor manufacturing a siloxane containing polymeric contact lens from amold, the method comprising: bringing two mold halves together to form alens mold; filling the mold with an uncured polymer; curing the polymerin the mold; separating the mold halves from one another; bringing themold half bearing the contact lens into contact with a cryogenicsubstance for a time sufficient to lower the temperature of the lens toa temperature sufficient to reduce adhesion between the lens and themold half to a point where removing the lens will not damage the lens;separating the lens from the mold half without the application ofexternal force to the lens; and recovering the lens.
 17. A methodaccording to claim 16 wherein the cryogenic substance is selected fromthe group consisting of liquid nitrogen, liquid helium and solid carbondioxide.
 18. A method according to claim 17 wherein the step ofseparating the lens from the mold half comprises bringing the mold halfbearing the lens into contact with a cryogenic substance for a timesufficient to lower the temperature of the lens to a temperaturesufficient to reduce adhesion between the lens and the mold half to apoint where the lens will fall from the mold half when the mold half isoriented above the lens.
 19. A method for extracting a polymeric contactlens from a mold, the method comprising: lowering the temperature of thelens to a temperature at which the lens will release from the moldwithout the application of external force to the lens the temperature ofthe lens being lowered using a cryogenic substance.
 20. The method ofclaim 19 wherein the step of lowering the temperature of the contactlens comprises directly contacting the contact lens with the cryogenicsubstance.
 21. The method of claim 20 wherein the cryogenic substance isselected from the group consisting of liquid nitrogen, liquid helium andsolid carbon dioxide.
 22. The method of claim 19 wherein the step oflowering the temperature of the contact lens comprises indirectlycooling the contact lens by contacting the mold with the cryogenicsubstance while the lens is in contact with the mold.
 23. The method ofclaim 22 wherein the cryogenic substance is selected from the groupconsisting of liquid nitrogen, liquid helium and solid carbon dioxide.24. The method of claim 19 wherein the contact lens comprises asiloxane-containing polymer.